Saylor.org's English Composition/Conjunctions

Conjunctions are words that connect two words, phrases, clauses or phrases together. Conjunctions can either be coordinating or subordinating. Coordinating conjunctions connect two equal words, clauses or sentences. Common coordinating conjunctions and their uses include:

• For presents a reason "I go on walks with my dog for it's healthy exercise."
• And presents non-contrasting item(s) or idea(s) "I walk my dog and play fetch with him."
• Nor presents a non-contrasting negative idea "Neither do I walk my dog nor do I play fetch with him."
• But presents a contrast or exception "I walk my dog but I never play fetch with him."
• Or presents an alternative item or idea "I can choose to walk my dog or play fetch with him."
• Yet presents a contrast or exception "I walk my dog, yet I refuse to play fetch with him."
• So presents a consequence "I walk my dog so we're both in good shape."

Subordinating conjunctions, also called subordinators, are conjunctions that conjoin an independent clause and a dependent clause. The most common subordinating conjunctions in the English language include after, although, as, as far as, as if, as long as, as soon as, as though, because, before, if, in order that, since, so, so that, than, though, unless, until, when, whenever, where, whereas, wherever, and while.

There is a long-held grammatical controversy that when writing, beginning a sentence with "and" "but" or "so" is unacceptable. Although there is no historical precedent for this to be considered incorrect, it is largely frowned upon.